December 19, 2012

ASCB 2012: Poles apart

On Tuesday at the ASCB annual meeting, I attended the
minisymposium on Cell Polarity, which addressed cell polarization and asymmetry
in several different contexts.

Jayme Dyer, from Danny Lew’s group, described how mating
budding yeast orient their growth toward a source of pheromones. Cdc42 is at
the heart of a positive feedback loop that builds a patch of polarity proteins
at the cell surface to orient cell growth. However, to successfully track the
chemoattractant gradient and, if necessary, allow cell reorientation, the
polarity patch “wanders” around the surface. Through a mix of computational and
experimental approaches, Dyer demonstrated that this wandering is driven by
vesicle trafficking that delivers Cdc42-free membrane to dilute the patch of
polarity proteins. Blocking patch wandering inhibits yeast cell’s ability to
reorient towards the source of chemoattractant.

Elsewhere in the session, Manuel Thery, who has previously
shown that plating cells on micropatterns can change the orientation of their
mitotic spindles by altering the distribution of cell adhesions, demonstrated
that micropatterns can also influence how cells segregate their chromatids, so
that one daughter preferentially inherits older DNA strands. Mayu Inada, from
Yukiko Yamashita’s laboratory, discussed how Drosophila germline stem cells check that they are oriented
correctly before entering mitosis, and Yves Barral gave a fascinating talk
describing how budding yeast asymmetrically segregate extrachromosomal ribosomal
DNA circles – aging factors that preferentially accumulate in mother cells instead
of being passed on to younger daughter cells.

This latter talk was certainly new to me and, over all, the
session did a great job of highlighting the many ways that cells demonstrate
asymmetry, and the variety of mechanisms that underlie these different processes.

biowrites content is distributed under the terms of an Attribution-Noncommercial-Share Alike-No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution-Noncommercial-Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).